X-ray Absorption Near-Edge Structure (XANES) at the O K-Edge of Bulk Co(3)O(4): Experimental and Theoretical Studies

We combine theoretical and experimental X-ray absorption near-edge spectroscopy (XANES) to probe the local environment around cationic sites of bulk spinel cobalt tetraoxide (Co [Formula: see text] O [Formula: see text]). Specifically, we analyse the oxygen K-edge spectrum. We find an excellent agreement between our calculated spectra based on the density functional theory and the projector augmented wave method, previous calculations as well as with the experiment. The oxygen K-edge spectrum shows a strong pre-edge peak which can be ascribed to dipole transitions from O [Formula: see text] to O [Formula: see text] states hybridized with the unoccupied [Formula: see text] states of cobalt atoms. Also, since Co [Formula: see text] O [Formula: see text] contains two types of Co atoms, i.e., Co [Formula: see text] and Co [Formula: see text] , we find that contribution of Co [Formula: see text] ions to the pre-edge peak is solely due to single spin-polarized [Formula: see text] orbitals ([Formula: see text] , [Formula: see text] , and [Formula: see text]) while that of Co [Formula: see text] ions is due to spin-up and spin-down polarized [Formula: see text] orbitals ([Formula: see text] and [Formula: see text]). Furthermore, we deduce the magnetic moments on the Co [Formula: see text] and Co [Formula: see text] to be zero and 3.00 [Formula: see text] respectively. This is consistent with an earlier experimental study which found that the magnetic structure of Co [Formula: see text] O [Formula: see text] consists of antiferromagnetically ordered Co [Formula: see text] spins, each of which is surrounded by four nearest neighbours of oppositely directed spins.